Not Applicable.
Not Applicable.
Reference to Microfiche Appendix
Not Applicable
1. Field of the Invention
This invention relates generally to electrical connectors and more specifically to high speed electrical connectors.
2. Description of Related Art
Electrical connectors are widely used in the manufacture of electronic systems because they allow the system to be built in separate pieces that can then be assembled. Board-to-board connectors are widely used because sophisticated electronic systems are usually fabricated on multiple printed circuit boards. To assemble the electronic system, the printed circuit boards are electrically connected.
In the description that follows, the invention will be illustrated as applied to a board to board connector. In particular, the invention will be illustrated in connection with a backplane-daughter card interconnection system. Many electronic systems, such as computer servers or telecommunications switches are built using a backplane and multiple xe2x80x9cdaughterxe2x80x9d cards. In such a configuration, the active circuitry of the electronic system is built on the daughter cards. For example, a processor might be built on one daughter card. A memory bank might be built on a different daughter card. The backplane provides signal paths that route electrical signals between the daughter cards.
Generally, electrical connectors are mounted to both the backplane and the daughter card. These connectors mate to allow electrical signals to pass between the daughter card and the backplane.
Because the electronic systems that use a backplane-daughter card configuration usually process much data, there is a need for the electrical connectors to carry much data. Furthermore, this data is generally transmitted at a high data rate. There is simultaneously a need to make the systems as small as possible. As a result, there is a need to have electrical connectors that can carry many high speed signals in a relatively small space. There is thus a need for high speed-high density connectors.
Several commercially available high-speed, high density electrical connectors are known. For example, U.S. Pat. No. 6,299,483 to Cohen et al. entitled High Speed High Density Electrical Connector is one example. Teradyne, Inc., the assignee of that patent, sells a commercial product called VHDM(copyright). Another example may be found in U.S. Pat. No. 6,409,543 to Astbury, et al. entitled Connector Molding Method and Shielded Waferized Connector Made Therefrom. Teradyne, Inc., the assignee of that patent, sells a commercial product called GbX(trademark). The foregoing patents arc hereby incorporated by reference.
Both of the above-described electrical connectors employ insert molding construction techniques, at least for the daughter card connectors. Subassemblies, called wafers, are formed around individual columns of signal contacts. The wafers are formed by molding a dielectric material around the metal signal contacts. The wafers are then stacked side by side to make a connector of the desired length.
One of the difficulties that results when a high density, high speed connector is made in this fashion is that the electrical conductors can be so close that there can be electrical interference between adjacent or nearby signal conductors. To reduce interference, and to otherwise provide desirable electrical properties, metal members are often placed between or around adjacent signal conductors. The metal acts as a shield to prevent signals carried on one conductor from creating xe2x80x9ccross talkxe2x80x9d on another conductor. The metal also impacts the impedance of each conductor, which can further contribute to desirable electrical properties.
Generally, the metal members are made from separate pieces of metal that are added to the connector. However, it has also been suggested that a metal coating be applied to the connector. Also, in some connectors, the base material of the housing is formed of metal, usually as a die cast part. Then, insulative members are inserted to preclude the signal conductors of the connector from being shorted by the metal housing.
A drawback of forming the shields from separate pieces of metal is that additional pieces are required to assemble the connector. The additional pieces increase the cost and complexity of manufacturing the connector. In some cases, shield pieces are stamped and formed to create tabs or projections that extend between adjacent signal conductors. This configuration reduces the number of separate pieces because the projections stay attached to the sheet, so only one additional piece is required. However, a drawback of forming a sheet with projections extending from it is that forming the projection leaves a hole in the sheet. Thus, while the projection increases shielding between signal conductors that are adjacent along a line running in one direction, leaving a hole in the shield sheet decreases shielding between signal conductors that are adjacent along a line running in an orthogonal direction. A further drawback of stamping and forming projections from a single shield member is that it is difficult to form projections that have bends or cornersxe2x80x94which are often needed to follow contours of signal contacts in some connectors, such as right angle connectors.
A drawback of coating metal onto a plastic is that there are no combinations of readily available and inexpensive metals and plastics that can be used. Either the metal does not adhere well to the plastic or the plastic lacks the desired thermal or mechanical properties needed to make a suitable connector. A further drawback of coating metal onto plastic is that available plating techniques are not selective. The portions of the connector housing which should not be conductive must be masked before the coating is applied. For example holes in the housing that hold signal contacts are often filled with plugs before coating, which are then removed after coating. A drawback of manufacturing connectors using a die cast metal housing is the complexity arising from the use of insulative inserts. Further, there is a limit to how thin features on a die cast part can be made. Generally, a die cast housing will have thicker parts. Using thicker housing parts is generally undesirable because it reduces the overall density of the connector. Die cast metals are more expensive than typical plastic parts.
It would be highly desirable to provide a connector with desirable electrical properties that is easy to manufacture and provides a high signal density.
With the foregoing background in mind, it is an object of the invention to provide a high speed, high density electrical connector that is easy to manufacture.
The foregoing and other objects are achieved in an electrical connector that is molded from different types of material to form at least two regions of distinct electrical properties. One region is formed from material filled with conducting material to alter the electrical properties.
In a preferred embodiment, an electrical connector having electrical conductors in a plurality of rows is provided, wherein each of the plurality of rows includes a housing and a plurality of electrical conductors. Each electrical conductor has a first contact end connectable to a printed circuit board, a second contact end and an intermediate portion therebetween that is disposed within the housing. The housing includes a first region surrounding each of the plurality of electrical conductors, the first region made of insulative material and extending substantially along the length of the intermediate portion of the electrical conductors. The housing also includes a second region adjacent the first region and extending substantially along the length of the intermediate portion of the electrical conductors. The second region is made of a material with a binder containing conductive fillers.